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Studying Cosmic acceleration and neutrino masses with DES. Outline DES: what is it and update + probes used Dark energy from DES. Neutrino masses from DES. Filipe Batoni Abdalla. Future Dark Energy Surveys. WFIRST. The Dark Energy Survey (DES). Proposal:

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Studying cosmic acceleration and neutrino masses with des http www darkenergysurvey org
Studying Cosmic acceleration and neutrino masses with DES.


  • DES: what is it and update + probes used

  • Dark energy from DES.

  • Neutrino masses from DES

Filipe BatoniAbdalla

The dark energy survey des
The Dark Energy Survey (DES)

  • Proposal:

    • Perform a 5000 sq. deg. survey of the southern galactic cap

    • Measure dark energy with 4 complementary techniques

  • New Instrument:

    • Replace the PF cage with a new 2.2 FOV, 520 Mega pixel optical CCD camera + corrector

  • Time scale:

    • Instrument Construction 2008-2011

  • Survey:

    • 525 nights during Oct.–Feb. 2011-2016

    • Area overlap with SPT SZ survey and VISTA VHS

Use the Blanco

4m Telescope

at the Cerro Tololo


Observatory (CTIO)

The des collaboration
The DES Collaboration

an international collaboration of ~100 scientists from ~20 institutions

US: Fermilab, UIUC/NCSA, University of Chicago,

LBNL, NOAO, University of Michigan, University of Pennsylvania, Argonne National Laboratory, Ohio State University, Santa-Cruz/SLAC Consortium

UK Consortium:

UCL, Cambridge, Edinburgh, Portsmouth, Sussex, Nottingham

Spain Consortium:


Brazil Consortium:

Observatorio Nacional, CBPF,Universidade Federal do Rio de Janeiro, Universidade Federal do Rio Grande do Sul


Standard model of cosmology dark energy dark matter exists no budget for neutrino mass
Standard model of cosmology:Dark energy & dark matter exists, No budget for neutrinomass:

Observational data

  • Type Ia Supernovae

  • Galaxy Clusters

  • Cosmic Microwave Background

  • Large Scale Structure

  • Gravitational Lensing

    Physical effects:

  • Geometry

  • Growth of Structure

Very brief overview on explaining the accelerated expansion

Cosmological constant



Dark Energy

modification of Einstein's gravity

String theory

Dark Energy : equation-of-state parameter w

Very Brief Overview on explaining the accelerated expansion


Des forecasts power of multiple techniques

DES Forecasts: Power of Multiple Techniques

w(z) =w0+wa(1–a) 68% CL



8=0.75, zmax=1.5,

WL mass calibration



(no bispectrum)


systematic errors only

Spatial curvature, galaxy bias


Planck CMB prior



DETF Figure of

Merit: inverse

area of ellipse

Stage II not

included here


Neutrino oscillations indicate they have mass!

But not on the absolute scale of mass…

For example…

  • Beta-decay kinematics


  • Neutrinoless double beta-decay


  • Cosmology!

Thomas, Abdalla, Lahav (2009)

Not just interesting physics but,

Age of precision Cosmology

an integral part of the cosmological model…

Neutrino mass…a test of LCDM

Des will also constrain the neutrino mass
DES will also constrain the neutrino mass

  • We have made simulations for this with Des photometric redshifts

  • We have also measured this from the current SDSS survey.

  • I will go through the assumptions and present the results from SDSS + forecasts for DES.

Tools: Photometric Redshifts

  • Photometric redshifts (photo-z’s) are determined from the fluxes of galaxies through a set of filters

    • May be thought of as low-resolution spectroscopy

  • Photo-z signal comes primarily from strong galaxy spectral features, like the 4000 Å break, as they redshift through the filter bandpasses

  • Photo-z calibrations is optimized using spectra.

Galaxy spectrum at 2 different redshifts, overlaid on griz and IR bandpasses

Cosmology with lrg s 1 photo z s and neural networks

Collister & Lahav 2004

Cosmology with LRG’s1- Photo-z’s and Neural networks:

  • Has an architecture: defined by a number of inputs/ outputs and nodes in hidden layers

  • Internally values range from 0 to 1 roughly

Looking at techniques in real data the 2slaq megazlrg
Looking at techniques in real data:The 2SLAQ & MegazLRG.

Abdalla et al 08

  • 2SLAQ galaxies selected from the SDSS.

  • Red galaxies z=0.4->0.7.

  • Good photo-z for LRG given large 4000A break.

  • 13000 galaxies from 2SLAQ. ~8000 for training ~5000 to calibrate the histogram.

  • MegaZ-LRG DR7: 3.3 Gpc^3 in volume (largest photo-z survey), > 700000 galaxies used.

  • Also use neural networks to separate stars from galaxies to better than 1% contamination of stars…


DES griz


+VHS JHKs on


enhances science reach

J 20.3

H 19.4

Ks 18.3

*Vista Hemisphere Survey

Galaxy Photo-z Simulations


10 Limiting Magnitudes

g 24.6

r 24.1

i 24.0

z 23.9

+2% photometric calibration

error added in quadrature

Z 23.8

Y 21.6

+Developed improved Photo-z & Error Estimates and robust methods of outlier rejection

Cunha, Lima, Frieman, Lin and Abdalla, Banerji. Lahav

ANNz; low depth survey: training

sets in place

Neutrino Physics - CMB

  • CMB is affected by neutrino physics

  • However degeneracies are large

  • CMB insensitive to neutrino masses smaller than 1eV as they become non-relativistic after the CMB is set up.

  • Does not consider the deflection spectrum

Neutrinos as dark matter
Neutrinos as Dark Matter

  • Neutrinos are natural DM candidates

  • They stream freely until non-relativistic (collisionless phase mixing)Neutrinos are HOT Dark Matter

  • First structures to be formed when Universe became matter -dominated

  • Ruled out by structure formation CDM

Neutrino Free Streaming



b, cdm

Measuring the clustering with photo z
Measuring the clustering with Photo-z



Photo-z distribution

Probes of Cosmology

Sloan Digital Sky Survey (SDSS)

+ Galaxy Clustering!

Luminous Red Galaxies (LRGS)

WMAP red: bound is ~1.3eV. (all 95%)

+ BAO+SNe: blue 0.69eV

+ MegaZ : yellow 0.65eV

+ BAO+SNe+MegaZ+HST: green 0.28eV

4 bins: 0.45 < z < 0.65

Max multipole l=300

MegaZ DR7

CMB + SN + BAO + SDSS LRGs + HST: < 0.28 eV (95% CL)

12 Parameters:

Thomaset al. [arXiv:0911.5291]

MegaZ DR7

Angular Power Spectra: Systematics - code comparison and training set extrapolation

DR6 catalogues - various codes

From e.g. Abdalla, Banerji, Lahav & Rashkov (2009)

1% smaller area

Bigger difference between template procedures than between template-training set

(1) Extrapolation seems valid

(2) No bias from ANNz

(3) No change in excess power

‘Systematics and Limitations’

Cosmology = check of systematics

Although we want tighter neutrino constraints We also want trustworthy neutrino constraints.


Galaxy Bias


Parameter Degeneracies

Model underlying matter power spectrum but measure the galaxy power spectrum

Scale dependence…mimic…?

Bias result or lose data

Quoted results assume cosmological constant cosmology

Perturbation theory/ N-body simulations

Degeneracy with w increases error bar

E.g. Saito et al 09

Brandbyge & Hannestad 09

L_max = 300 => 0.28 eV

L_max = 200 => 0.34 eV

Linear bias is a good fit, so more parameters cannot be justified. Future surveys will be able to say something more here…

Bounds reduced by ~10% if more params…

In the Future…

The Dark Energy Survey (DES)

Galaxy Bias


Parameter Degeneracies

Better modelling!

Forecast for Galaxy Clustering + Planck: < 0.12 eV

E.g. Lahav, Kiakotou, Abdalla and Blake - arXiv: 0910.4714

This combination will be 5 times more constraining than the WMAP + MegaZ equivalent

Total neutrino mass des vs katrin m 0 1 ev m 0 6 ev
Total Neutrino Mass DESvs.KATRIN M< 0.1 eVM < 0.6 eV


Goal: 0.05 eV but most importantly we might put the cosmological model to the test OR have a good stab at measuring the nu_mass!

Other cosmological probes of the neutrino mass: weak lensing, CMB lensing, etc…


  • DES under construction:

    • Lenses being polished

    • CCD’s being tested

    • Should have first light late next year.

  • Science predicts a increase in our knowledge in w0-wa plane.

  • Also increase in our knowledge in the neutrino mass:

    • Same experiment done on SDSS LRG’s m_nu < 0.28eV

    • For DES m_nu < 0.12eV with Planck only.

    • All these have to be taken with a pinch of salt… but… hopefully we will either pin down the neutrino mass or put the cosmological model to strain.